The invention disclosed herein pertains to a device wherein a plurality of information containing generally rectangular transparency panels are joined at their edges to form equilateral triangular units. Each transparency panel in a unit contains a portion of one of three pictures or scenes. The hollow triangular units are juxtaposed to each other and are adapted for being driven rotationally in synchronism such that when the transparencies that contain components of a particular picture become coplanar, the entire scene or picture becomes visible and intelligible to a viewer. The triangular units each rotate about an elongated light-emitting tube or lamp which illuminates the transparencies from the back to make them visible from the front when they are coplanar.
A sign of this general type is shown in U.S. Pat. No. 4,381,616 and in U.S. patent application Ser. No. 07,957,719, filed Oct. 7, 1992, which is now U.S. Pat. No. 5,315,776, owned by the Assignee of this application.
In display devices of the type outlined above, it is important that when the transparency panels composing a scene are coplanar, the joints between them are minimally visible at close viewing range and are substantially invisible at customary and expected viewing distances. The matter of getting acceptably inconspicuous joints between display panels has been problematical for designers. Of course, minimally visible joints between panels could be achieved if precision metal bearings were used in the rotational structure of the triangular transparency units and, if everything else in the display device were held to close tolerances, but these practices would raise the cost of the devices to an extent that they would not be commercially viable. Even more importantly, it is necessary to have a low cost and low price design that maintains joint invisibility after the display device is used for a long time.
Display devices of the type under consideration are frequently positioned at the point of sale of products, and they may be integrated with a replica of a product or associated with a display of products to which a merchandiser or tavern keeper, for example, would like to attract the attention of customers.